High-resolution photoelectron spectroscopy of vibrationally excited TiO2 anions

High resolution photoelectron spectra of TiO 2 − excited to its 𝑣 3 = 1 state were obtained via slow electron velocity-map imaging of cryogenically cooled anions (cryo-SEVI). To determine the 𝑣 3 (antisymmetric stretch) anion frequency, growth and depletion of various features in the cryo-SEVI spectrum were monitored over a range of infrared (IR) excitation energies. Photoelectron scans were taken at an IR pre-excitation energy of 918 cm −1 and yielded a ~6% depletion of features in the ground state cryo-SEVI spectra as well as new hot and sequence bands based on the 3 1 0 and 3 1 1 transitions, respectively. By monitoring hot band intensities as a function of IR laser frequency, the rotational profile of the 𝑣 3 = 0 − 1 transition was mapped out and found to be centered at 914(7) cm −1 . The observed hot bands are Franck-Condon forbidden and arise from Herzberg-Teller coupling with the à 1 B 2 neutral excited state, similar to what was observed in the cryo-SEVI spectra of TiO 2 − . The results from this IR cryo-SEVI experiment lay the groundwork for future investigations of larger bare and complexed transition metal oxide clusters.